Nostoc Sp Research Articles

The effect of different species of cyanobacteria on the rice yield and nitrogen use efficiency under different levels of nitrogen fertilizer on Alluvial West Java

Cyanobacteria or blue-green algae play an important role in rice cultivation. Nitrogen-fixing bacteria Cyanobacteria are found in rice fields, some of which can fix N2 up to 30%, produce some phytohormones, vitamins, amino acids, and organic acids increase soil fertility and rice productivity. The study was conducted in Alluvials wetland rice in Jatitujuh, Majalengka Regency, West Java. This research aimed to analyze the influence of cyanobacteria in increasing rice yield and the efficiency of inorganic N fertilizers. The study was arranged in a randomized block design with two factors. The first factor was the cyanobacteria formula, i.e.: (1) without cyanobacteria, (2) Pseudanabaena sp.+Chlorogloea sp., (3) Pseudanabaena sp.+Nostoc sp., (4) Chlorogloea sp.+Nostoc sp. The second factor was the dose of N fertilizer (0%, 50%, 75% and 100%). The highest rice yield obtained by Chlorogloea sp.+Nostoc sp with 100% N, increased by 14.75%. Application of Pseudanabaena sp. + Nostoc sp. was increased rice grain yield and straw biomass by 11.47% and 37.49%, reduced N fertilizer by 25 to 50%, and increased nutrient uptake of N, P, K by 43.73%, 34.80 %, 34.40%. Using cyanobacteria is a promising strategy to increase rice yield and reduce chemical fertilizers.

Anti-Inflammatory, Antioxidant, and Wound-Healing Properties of Cyanobacteria from Thermal Mud of Balaruc-Les-Bains, France: A Multi-Approach Study.

Background: The Balaruc-les-Bains’ thermal mud was found to be colonized predominantly by microorganisms, with cyanobacteria constituting the primary organism in the microbial biofilm observed on the mud surface. The success of cyanobacteria in colonizing this specific ecological niche can be explained in part by their taxa-specific adaptation capacities, and also the diversity of bioactive natural products that they synthesize. This array of components has physiological and ecological properties that may be exploited for various applications. Methods: Nine cyanobacterial strains were isolated from Balaruc thermal mud and maintained in the Paris Museum Collection (PMC). Full genome sequencing was performed coupled with targeted and untargeted metabolomic analyses (HPLC-DAD and LC-MS/MS). Bioassays were performed to determine antioxidant, anti-inflammatory, and wound-healing properties. Results: Biosynthetic pathways for phycobiliproteins, scytonemin, and carotenoid pigments and 124 metabolite biosynthetic gene clusters (BGCs) were characterized. Several compounds with known antioxidant or anti-inflammatory properties, such as carotenoids, phycobilins, mycosporine-like amino acids, and aeruginosins, and other bioactive metabolites like microginins, microviridins, and anabaenolysins were identified. Secretion of the proinflammatory cytokines TNF-α, IL-1β, IL-6, and IL-8 appeared to be inhibited by crude extracts of Planktothricoides raciborskii PMC 877.14, Nostoc sp. PMC 881.14, and Pseudo-chroococcus couteii PMC 885.14. The extract of the Aliinostoc sp. PMC 882.14 strain was able to slightly enhance migration of HaCat cells that may be helpful in wound healing. Several antioxidant compounds were detected, but no significant effects on nitric oxide secretion were observed. There was no cytotoxicity on the three cell types tested, indicating that cyanobacterial extracts may have anti-inflammatory therapeutic potential without harming body cells. These data open up promising uses for these extracts and their respective molecules in drugs or thermal therapies.

Effects of Modification of Light Parameters on the Production of Cryptophycin, Cyanotoxin with Potent Anticancer Activity, in Nostoc sp.

Cryptophycin-1 is a cyanotoxin produced by filamentous cyanobacteria. It has been evaluated as an anticancer agent with great potential. However, its synthesis provides insufficient yield for industrial use. An alternative solution for metabolite efficient production is to stress cyanobacteria by modifying the environmental conditions of the culture (Nostoc sp. ATCC 53789). Here, we examined the effects of light photoperiod, wavelength, and intensity. In light photoperiod, photoperiods 24:0 and 16:8 (light:dark) were tested while in wavelength, orange-red light was compared with blue. Medium, high, and very high light intensity experiments were performed to test the effect of light stress. For a 10-day period, growth was measured, metabolite concentration was calculated through HPLC, and the related curves were drawn. The differentiation of light wavelength had a major effect on the culture, as orange-red filter contributed to noticeable increase in both growth and doubled the cyanotoxin concentration in comparison to blue light. Remarkably, constant light provides higher cryptophycin yield, but slightly lower growth rate. Lastly, the microorganism prefers medium light intensities for both growth and metabolite expression. The combination of these optimal conditions would contribute to the further exploitation of cryptophycin.

Cd(II) sorption by Nostoc sp. JRD1: Kinetic, thermodynamic and isotherm studies

The present work describes the biosorption of Cd 2 + by a cyanobacterium isolated from water of an effluent reservoir of Hindustan Paper Corporation Limited, Jagiroad, India polluted with different heavy metal ions. The novelty of the study lies in the fact that an extensive literature search did not yield any report of biosorption by any cyanobacterium isolated from paper mill effluent. The molecular identification technique established the cyanobacterium as a Nostoc sp. and was named Nostoc sp. JRD1. The organism showed relatively high tolerance to Cd 2 + as a 24 h Cd 2 + (0.5 ppm) exposure showed no significant changes in its morphology and ultrastructure under bright-field, scanning and transmission microscopic study. Cd 2 + binding to its cell surface was confirmed by SEM-EDX investigation and FTIR analysis identified the functional groups involved in Cd 2 + binding. Cd 2 + biosorption by live biomass of the organism from aqueous solution was a function of initial inoculum size and metal ion concentration, pH, temperature and shaking rate and under optimized conditions the organism biosorbed 94% Cd 2 + from a solution supplied with 0.5 ppm Cd 2 + within 24 h. Of this total removed Cd 2 + , 89.5% was adsorbed on the cell surfaces while 7.2% was internalized. Kinetic study revealed Cd 2 + biosorption to be instantaneous (5–30 min) and fitted best in the pseudo-first-order kinetic model with q e cal value of 41.8 mg/g. Thermodynamic study indicated the process of biosorption as energetically favorable with a negative Δ G value and was exothermic in nature. Cd 2 + biosorption followed Langmuir isotherm best with a R 2 value of 0.98, and a maximum biosorption capacity, Q max of 24.7 mg/g. Almost similar Cd 2 + removal (92%) was found in a photo-bioreactor study compared to the removal scenario in a small conical flask (94%). The various outcomes of the study suggested that live Nostoc sp. JRD1 biomass is extremely suitable as biosorbent for removal of Cd 2 + from contaminated waters. • Morphological and ultrastructural studies confirmed Cd 2+ tolerance of Nostoc sp. JRD1. • The isolate could remove 94% Cd 2+ from a solution containing 0.5 ppm Cd 2+ . • Kinetic, thermodynamic & biosorption studies showed Cd 2+ sorption to be favorable. • Conditions Optimization enhanced biosorption percentage significantly. • Scanty information on any cyanobacteria isolated from paper mill effluent.

Lethal Mechanisms of Nostoc-Synthesized Silver Nanoparticles Against Different Pathogenic Bacteria.

BackgroundIncreasing antibiotic resistance and the emergence of multidrug-resistant (MDR) pathogens have led to the need to develop new therapeutic agents to tackle microbial infections. Nano-antibiotics are a novel generation of nanomaterials with significant antimicrobial activities that target bacterial defense systems including biofilm formation, membrane permeability, and virulence activity.PurposeIn addition to AgNO3, the current study aimed to explore for first time the antibacterial potential of silver nanoparticles synthesized by Nostoc sp. Bahar_M (N-SNPs) and their killing mechanisms against Streptococcus mutans, methicillin-resistant Staphylococcus aureus, Escherichia coli, and Salmonella typhimurium.MethodsPotential mechanisms of action of both silver species against bacteria were systematically explored using agar well diffusion, enzyme (lactate dehydrogenase (LDH) and ATPase) and antioxidant (glutathione peroxidase and catalase) assays, and morphological examinations. qRT-PCR and SDS-PAGE were employed to investigate the effect of both treatments on mfD, flu, and hly gene expression and protein patterns, respectively.ResultsN-SNPs exhibited greater biocidal activity than AgNO3 against the four tested bacteria. E. coli treated with N-SNPs showed significant surges in LDH levels, imbalances in other antioxidant and enzyme activities, and marked morphological changes, including cell membrane disruption and cytoplasmic dissolution. N-SNPs caused more significant upregulation of mfD expression and downregulation of both flu and hly expression and increased protein denaturation compared with AgNO3.ConclusionN-SNPs exhibited significant inhibitory potential against E. coli by direct interfering with bacterial cellular structures and/or enhancing oxidative stress, indicating their potential for use as an alternative antimicrobial agent. However, the potential of N-SNPs to be usable and biocompatible antibacterial drug will evaluate by their toxicity against normal cells.

Rapid Transcriptional Reprogramming Triggered by Alteration of the Carbon/Nitrogen Balance Has an Impact on Energy Metabolism in Nostoc sp. PCC 7120.

Nostoc (Anabaena) sp. PCC 7120 is a filamentous cyanobacterial species that fixes N2 to nitrogenous compounds using specialised heterocyst cells. Changes in the intracellular ratio of carbon to nitrogen (C/N balance) is known to trigger major transcriptional reprogramming of the cell, including initiating the differentiation of vegetative cells to heterocysts. Substantial transcriptional analysis has been performed on Nostoc sp. PCC 7120 during N stepdown (low to high C/N), but not during C stepdown (high to low C/N). In the current study, we shifted the metabolic balance of Nostoc sp. PCC 7120 cultures grown at 3% CO2 by introducing them to atmospheric conditions containing 0.04% CO2 for 1 h, after which the changes in gene expression were measured using RNAseq transcriptomics. This analysis revealed strong upregulation of carbon uptake, while nitrogen uptake and metabolism and early stages of heterocyst development were downregulated in response to the shift to low CO2. Furthermore, gene expression changes revealed a decrease in photosynthetic electron transport and increased photoprotection and reactive oxygen metabolism, as well a decrease in iron uptake and metabolism. Differential gene expression was largely attributed to change in the abundances of the metabolites 2-phosphoglycolate and 2-oxoglutarate, which signal a rapid shift from fluent photoassimilation to glycolytic metabolism of carbon after transition to low CO2. This work shows that the C/N balance in Nostoc sp. PCC 7120 rapidly adjusts the metabolic strategy through transcriptional reprogramming, enabling survival in the fluctuating environment.

Green synthesis of AgCl/Ag3PO4 nanoparticle using cyanobacteria and assessment of its antibacterial, colorimetric detection of heavy metals and antioxidant properties.

In this study, the extract of two strains of cyanobacteria was used for the synthesis of silver nanoparticles (NPs). UV-vis spectroscopy, X-ray diffraction, dynamic light scattering and field emission scanning electron microscopy (FESEM) analyses were carried out to characterise the NPs. The antioxidant activity and heavy metal detection properties were investigated; moreover, their minimum inhibitory concentration and minimum bactericidal concentration against the multi-drug resistant bacteria were determined. The most abundant materials in these extracts were carbohydrates, so the biosynthesis of NPs using exopolysaccharide (EPS) was also investigated. The surface plasmon resonance of NPs had a peak at 435 nm and EPS NPs at 350-450 nm. The NPs produced by Nostoc sp. IBRC-M5064 extract revealed the face-centred cubic (fcc) structure of AgCl, while NPs of N. pruniforme showed the fcc crystalline structure of Ag3PO4 and AgCl. The FESEM showed the spherical shape of these NPs. The AgCl/Ag3PO4 colloid, in comparison with AgCl, showed better antioxidant activity and antibacterial effect. The heavy metal detection analysis of NPs revealed that the NPs of both stains involved in Hg (NO3)2 detection.

NsiR3, a nitrogen stress-inducible small RNA, regulates proline oxidase expression in the cyanobacterium Nostoc sp. PCC 7120.

NsiR3 (nitrogen stress-inducible RNA 3) is a small noncoding RNA strongly conserved in heterocyst-forming cyanobacteria. In Nostoc sp. PCC 7120, transcription of NsiR3 is induced by nitrogen starvation and depends on the global nitrogen regulator NtcA. A conserved NtcA-binding site is centered around position -42.5 with respect to the transcription start site of NsiR3 homologs, and NtcA binds invitro to a DNA fragment containing this sequence. In the absence of combined nitrogen, NsiR3 expression is induced in all cells along the Nostoc filament but much more strongly in heterocysts, differentiated cells devoted to nitrogen fixation. Co-expression analysis of transcriptomic data obtained from microarrays hybridized with RNA obtained from Nostoc wild-type or mutant strains grown in the presence of ammonium or in the absence of combined nitrogen revealed that the expression profile of gene putA (proline oxidase) correlates negatively with that of NsiR3. Using a heterologous system in Escherichiacoli, we show that NsiR3 binds to the 5'-UTR of putA mRNA, resulting in reduced expression of a reporter gene. Overexpression of NsiR3 in Nostoc resulted in strong reduction of putA mRNA accumulation, further supporting the negative regulation of putA by NsiR3. The higher expression of NsiR3 in heterocysts versus vegetative cells of the N2 -fixing filament could contribute to the previously described absence of putA mRNA and of the catabolic pathway to produce glutamate from arginine via proline specifically in heterocysts. Post-transcriptional regulation by NsiR3 represents an indirect NtcA-operated regulatory mechanism of putA expression. DATABASE: Microarray data are available in GEO database under accession numbers GSE120377 and GSE150191.

Phosphorus Feast and Famine in Cyanobacteria: Is Luxury Uptake of the Nutrient Just a Consequence of Acclimation to Its Shortage?

To cope with fluctuating phosphorus (P) availability, cyanobacteria developed diverse acclimations, including luxury P uptake (LPU)—taking up P in excess of the current metabolic demand. LPU is underexplored, despite its importance for nutrient-driven rearrangements in aquatic ecosystems. We studied the LPU after the refeeding of P-deprived cyanobacterium Nostoc sp. PCC 7118 with inorganic phosphate (Pi), including the kinetics of Pi uptake, turnover of polyphosphate, cell ultrastructure, and gene expression. The P-deprived cells deployed acclimations to P shortage (reduction of photosynthetic apparatus and mobilization of cell P reserves). The P-starved cells capable of LPU exhibited a biphasic kinetic of the Pi uptake and polyphosphate formation. The first (fast) phase (1–2 h after Pi refeeding) occurred independently of light and temperature. It was accompanied by a transient accumulation of polyphosphate, still upregulated genes encoding high-affinity Pi transporters, and an ATP-dependent polyphosphate kinase. During the second (slow) phase, recovery from P starvation was accompanied by the downregulation of these genes. Our study revealed no specific acclimation to ample P conditions in Nostoc sp. PCC 7118. We conclude that the observed LPU phenomenon does not likely result from the activation of a mechanism specific for ample P conditions. On the contrary, it stems from slow disengagement of the low-P responses after the abrupt transition from low-P to ample P conditions.

Cold adaptation in drylands: transcriptomic insights into cold-stressed Nostoc flagelliforme and characterization of a hypothetical gene with cold and nitrogen stress tolerance.

Environmental stressors, especially low temperature, are very common on the earth's dryland systems. Terrestrial cyanobacteria have evolved with cold adaptability in addition to extreme dryness and high irradiation resistance. The dryland soil surface-dwelling species, Nostoc flagelliforme, serves as a potential model organism to gain insights into cyanobacterial cold adaptation. In this study, we performed transcriptomic analysis of N. flagelliforme samples in response to low temperature. The results revealed that the biological processes, such as terpenoid biosynthetic process, oxidoreductase activity, carbohydrate metabolism, biosynthesis of secondary metabolites, lipid and nitrogen metabolism, were significantly and dynamically changed during the cold stress. It was noteworthy that the transcription of the denitrification pathway for ammonia accumulation was enhanced, implying an importance for nitrogen utilization in stress resistance. In addition, characterization of a cold-responsive hypothetical gene csrnf1 found that it could greatly improve the cold-resistant performance of cells when it was heterologously expressed in transgenic Nostoc sp. PCC 7120. It was also found that csrnf1 transgenic strain exhibited resistance to nitrogen-deficient environmental stress. Considering that dryland cyanobacteria have to cope with low temperature on infertile soils, this study would enrich our understanding on the importance of multifunction of the genes for environmental cold adaptation in drylands.

Tolerance of Dried Cells of a Terrestrial Cyanobacterium, Nostoc sp. HK-01 to Temperature Cycles, Helium-ion Beams, Ultraviolet Radiation (172 and 254 nm), and Gamma Rays: Primitive Analysis for Space Experiments

Tolerance of Dried Cells of a Terrestrial Cyanobacterium, Nostoc sp. HK-01 to Temperature Cycles, Helium-ion Beams, Ultraviolet Radiation (172 and 254 nm), and Gamma Rays: Primitive Analysis for Space Experiments

Dominance of potentially toxic cyanobacteria on the waterfront of Santarém, Tapajós River, Brazilian Amazon

The present study carried out an evaluation of physicochemical parameters of waters from the low Tapajós river, and the identification of dominant cyanobacteria in the blooms that occurred in a transect bordering the Santarém city waterfront, in the State of Pará, Brazilian Amazon. Five (5) sampling stations were selected along the waterfront (RT-E1, RT-E2, RT-E3, RT-E4, RTE5), where water, phytoplankton and general environmental data were collected during 10 field campaigns, at intervals of 48 hours, between January 13th and 31st 2015, at the very beginning of the rainy season. The sample collections were conducted at an average depth of 2.3 meters, always early in the morning and following the procedures of the Collection and Preservation Guide and Water Samples of the Brazilian National Water Agency. Quantitative analyses of the physicochemical parameters were performed, namely: hydrogenionic potential (pH); water temperature (ºC); turbidity (NTU); electrical conductivity (EC); Dissolved Oxygen (DO); nitrate (NO-3); nitrite (NO-2); ammonium ion (NH4); ammonia (NH3); orthophosphate (PO43-); phosphate (P2O5); phosphorus (P); iron (Fe) and chlorophyll a (Chlo a). General descriptive statistics were calculated. For counting of individuals, the efficiency was superior to 80%, reaching a total of 3,910 individuals, from which 38% are species of the Cyanophyta division. The following species were dominant: Synechocystis aquatilis Microcystis aeruginosa, Dolichospermum spiroides, Nostoc sp. Except for S. aquatilis, all the others are cyanotoxin producers that can be released into the water after cell disruption. The presence of cyanobacteria potentially producing cyanotoxins is of concern and should be considered in the diagnosis of waterborne diseases, such as hepatic infections that affect the riverine population of the Tapajós river.

Physiological and Biochemical Response of a Hot-Spring Cyanobacterium Nostoc Sp. Strain HKAR-2 to Aluminum Toxicity

Aluminum is an undesirable water pollutant released by water treatment plants and metal processing industries that exhibit enormous toxic effects on water bodies. In the present study, we have investigated the effects of aluminum toxicity on the physiological and biochemical behavior of a hot-spring cyanobacterium Nostoc sp. strain HKAR-2. The growth of cyanobacterium was declined up to 33% by increasing aluminum concentration from 0.2 to 0.6 mM at pH 7.5 as compared to control (non-treated). However, the growth had further declined up to 87 and 92% by decreasing the pH to 6.0 and 5.0, respectively, as compared to control (pH 7.5) after 12 days of treatment. The amount of protein, chlorophyll, mycosporine-like amino acids, phycobiliproteins, extracellular and intracellular macronutrients such as phosphate and nitrate contents, and nitrate reductase activity was also declined at pH 7.5 as compared to non-treated control. In addition, aluminum also altered the sodium and potassium ions in both extracellular and intracellular environments. There was an increase in the activity of antioxidative enzymes such as catalase (CAT), superoxide dismutase (SOD), and ascorbic peroxidase (APX) ranging from 58, 79, and 40%, respectively, at 0.6 mM aluminum. The increase in intracellular concentration of aluminum was directly proportional to the inhibition of cyanobacterial growth at pH 7.5. In conclusion, aluminum showed acute toxicity on the hot-spring cyanobacterium Nostoc sp. strain HKAR-2, which indicates that aluminum may adversely affect the microbiota of hot-spring habitats.

The interplay between chromophore and protein determines the extended excited state dynamics in a single-domain phytochrome

Phytochromes are a diverse family of bilin-binding photoreceptors that regulate a wide range of physiological processes. Their photochemical properties make them attractive for applications in optogenetics and superresolution microscopy. Phytochromes undergo reversible photoconversion triggered by the Z ⇄ E photoisomerization about the double bond in the bilin chromophore. However, it is not fully understood at the molecular level how the protein framework facilitates the complex photoisomerization dynamics. We have studied a single-domain bilin-binding photoreceptor All2699g1 (Nostoc sp. PCC 7120) that exhibits photoconversion between the red light-absorbing (Pr) and far red-absorbing (Pfr) states just like canonical phytochromes. We present the crystal structure and examine the photoisomerization mechanism of the Pr form as well as the formation of the primary photoproduct Lumi-R using time-resolved spectroscopy and hybrid quantum mechanics/molecular mechanics simulations. We show that the unusually long excited state lifetime (broad lifetime distribution centered at ∼300 picoseconds) is due to the interactions between the isomerizing pyrrole ring D and an adjacent conserved Tyr142. The decay kinetics shows a strongly distributed character which is imposed by the nonexponential protein dynamics. Our findings offer a mechanistic insight into how the quantum efficiency of the bilin photoisomerization is tuned by the protein environment, thereby providing a structural framework for engineering bilin-based optical agents for imaging and optogenetics applications.

NsiR1, a small RNA with multiple copies, modulates heterocyst differentiation in the cyanobacterium Nostoc sp. PCC 7120.

Upon nitrogen starvation, filamentous cyanobacteria develop heterocysts, specialized cells devoted to the fixation of atmospheric nitrogen. Differentiation of heterocyst at semi-regular intervals along the filaments requires complex structural and functional changes that are under the control of the master transcriptional regulator HetR. NsiR1 (nitrogen stress-induced RNA 1) is a HetR-dependent non-coding RNA that is expressed specifically in heterocysts from a very early stage of differentiation. In the genome of Nostoc sp. PCC 7120 there are 12 tandem copies of nsiR1 (nsiR1.1 to nsiR1.12), seven of them with identical sequence (nsiR1.3 to nsiR1.9) and the others slightly divergent. nsiR1.1 is transcribed antisense to the 5' UTR of hetF, a gene required for heterocyst development. Here, we show that binding of NsiR1.1 inhibits translation of the hetF mRNA by inducing structural changes in its 5' UTR. Altered levels of NsiR1 result in different phenotypic alterations including enlarged cell size and delayed heterocyst development that could be related to a reduced amount of HetF.

Nitrogen-fixing cyanobacteria as a potential resource for efficient biodiesel production

The incessant utilization of non-renewable energy sources persistently pollutes the earth's atmosphere and thus requires the immediate substitution by renewable energy sources such as biofuel. In this study, several nitrogen-fixing cyanobacteria are screened for biodiesel production on the basis of biomass productivity, lipid productivity, lipid profiling, and harvesting potential. The assessment performed led to the identification of Nostoc sp. MCC41, a nitrogen ficxing cyanobacteria as promising species (0.39 day−1 specific growth rate, biomass productivity of 540 mg L−1 day−1, lipid productivity of 84 mg L−1 day−1 and 15.7% lipid content). A simple filtration experiment shows that almost 81% of the biomass of Nostoc sp. MCC41 is harvested without flocculation aid, while only 23–45% of the green algae (control) could be filtered. Based on the results, further optimization of Nostoc sp. MCC41 is carried out. The optimum light intensity to attain the highest lipid productivity is found to be 54 μmol photon m−2 s−1. Continuous illumination rather than other photoperiods is superior in terms of lipid productivity. Moreover, Nostoc sp. MCC41 could grow under mixotrophic conditions revealing the potential towards an organic carbon-rich wastewater treatment. At 0.5% glucose, the Nostoc sp. MCC41 exhibited nearly five-fold increase in biomass productivity when compared to the phototrophic conditions. Lipid profiling uncovered that Nostoc sp. MCC41 has a high concentration of palmitic acid, indicating its suitability for biodiesel. Given its easy mode of harvesting, ability to grow under mixotrophic condition, and ability to fix atmospheric nitrogen, Nostoc sp. MCC41 can be considered as a potential and eco-friendly resource for efficient biodiesel production.

Nutrient removal from the centrate of anaerobic digestion of high ammonium industrial wastewater by a semi-continuous culture of Arthrospira sp. and Nostoc sp. PCC 7413

The feasibility of the semi-continuous cultivation of Arthrospira (Spirulina) sp. and Nostoc sp. PCC 7413, using the centrate from the anaerobic digestion of wastewater from a seafood canning industry as a nutrient source, was assessed. Semi-continuous cultures were carried out in aerated tubular culture units of 250 mL by replacing a 10–20% of the volume with the centrate every 2 days. Growth, ammonium, and nitrate removal were monitored, as well as phycobiliprotein and protein production by Arthrospira sp. and released exopolysaccharides production by Nostoc sp. PCC 7413. The ammonium removal efficiency by Arthrospira sp. was 84.9 ± 1.9% in a culture maintained with an ammonium concentration of 11.3 mM. Lower ammonium concentrations (4.9 mM) could be applied to Nostoc sp. PCC 7413, reaching similar relative removal efficiency (84.1%). Taking into account the high ammonium stripping that occurs at the high pH required in Arthrospira sp. cultures, results indicate a better nutrient removal by Nostoc sp., although Arthrospira sp. is more suitable for working at high ammonium concentrations. Since all the ammonium was removed during the first 24 h for both species, much lower residence time could be supported by the cultures. High concentrations of protein (2.5 ± 0.2 mg mL−1), phycobiliprotein (allophycocyanin, 84.3 ± 10.2 mg g−1; phycocyanin, 73.7 ± 7.7 mg g−1) were obtained by Arthrospira sp. cultures. A high concentration of released exopolysaccharides (962.7 ± 26.7 mg L−1) was also obtained for Nostoc sp. PCC 7413 when cultured in the anaerobic centrate. The results indicate the possibility of the use of filamentous cyanobacteria for the treatment of industrial effluents rich in ammonium, with different possibilities of valorization of the biomass produced.

Cytokinins affect the akinete-germination stage of a terrestrial filamentous cyanobacterium, Nostoc sp. HK-01

Cyanobacteria are distributed globally in the sea, fresh water, and land. Akinetes (dormant cells) of cyanobacteria are highly resistant to dry conditions, contributing to the survival of terrestrial cyanobacteria. However, the substances that regulate akinete dormancy and germination have not been elucidated. The present study investigated the effects of the phytohormone cytokinin (CK), on the germination stage of a terrestrial filamentous cyanobacterium, Nostoc sp. HK-01. In the cell suspensions of Nostoc sp. HK-01, isopentenyladenine (iP), isopentenyladenosine (iPR), cis-zeatin (cZ), cis-zeatinriboside (cZR), trans-zeatin (tZ), and a trace amount of trans-zeatinriboside (tZR) were identified, according to their retention times and multiple reaction monitoring (MRM) transitions, using high performance liquid chromatography and electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS). Product ion scans also identified iP, iPR, cZ, and cZR. The present study established an isolation method for the dormant Nostoc akinetes, and then treated them with CKs. iP and tZ promoted the germination of akinetes, while cZ did not. S-4893, which is a CK antagonist, inhibited germination and the promotive activity of the applied iP. The results strongly suggest that cyanobacteria have a very similar perception system to plants, and that they regulate the dormancy and germination of their own cells and/or other cells via CKs. The production of CKs by several species of cyanobacteria was previously reported. However, this is the first investigation showing the role of phytohormones in the dormant cell physiology of cyanobacteria.

Proteomic Insights into Starvation of Nitrogen-Replete Cells of Nostoc sp. PCC 7120 under β-N-Methylamino-L-Alanine (BMAA) Treatment.

All cyanobacteria produce a neurotoxic non-protein amino acid β-N-methylamino-L-alanine (BMAA). However, the biological function of BMAA in the regulation of cyanobacteria metabolism still remains undetermined. It is known that BMAA suppresses the formation of heterocysts in diazotrophic cyanobacteria under nitrogen starvation conditions, and BMAA induces the formation of heterocyst-like cells under nitrogen excess conditions, by causing the expression of heterocyst-specific genes that are usually “silent” under nitrogen-replete conditions, as if these bacteria receive a nitrogen deficiency intracellular molecular signal. In order to find out the molecular mechanisms underlying this unexpected BMAA effect, we studied the proteome of cyanobacterium Nostoc sp. PCC 7120 grown under BMAA treatment in nitrogen-replete medium. Experiments were performed in two experimental settings: (1) in control samples consisted of cells grown without the BMAA treatment and (2) the treated samples consisted of cells grown with addition of an aqueous solution of BMAA (20 µM). In total, 1567 different proteins of Nostoc sp. PCC 7120 were identified by LC-MS/MS spectrometry. Among them, 80 proteins belonging to different functional categories were chosen for further functional analysis and interpretation of obtained proteomic data. Here, we provide the evidence that a pleiotropic regulatory effect of BMAA on the proteome of cyanobacterium was largely different under conditions of nitrogen-excess compared to its effect under nitrogen starvation conditions (that was studied in our previous work). The most significant difference in proteome expression between the BMAA-treated and untreated samples under different growth conditions was detected in key regulatory protein PII (GlnB). BMAA downregulates protein PII in nitrogen-starved cells and upregulates this protein in nitrogen-replete conditions. PII protein is a key signal transduction protein and the change in its regulation leads to the change of many other regulatory proteins, including different transcriptional factors, enzymes and transporters. Complex changes in key metabolic and regulatory proteins (RbcL, RbcS, Rca, CmpA, GltS, NodM, thioredoxin 1, RpbD, ClpP, MinD, RecA, etc.), detected in this experimental study, could be a reason for the appearance of the “starvation” state in nitrogen-replete conditions in the presence of BMAA. In addition, 15 proteins identified in this study are encoded by genes, which are under the control of NtcA—a global transcriptional regulator—one of the main protein partners and transcriptional regulators of PII protein. Thereby, this proteomic study gives a possible explanation of cyanobacterium starvation under nitrogen-replete conditions and BMAA treatment. It allows to take a closer look at the regulation of cyanobacteria metabolism affected by this cyanotoxin.

Application of Nostoc sp. for hexavalent chromium [Cr(VI)] removal: planktonic and biofilm

ABSTRACT The bio-sorption is the using of biological biomasses, live or dead form, for heavy metals removal from polluted wastewater. In the current work, live planktonic Nostoc sp. cells were used for hexavalent Chromium [Cr(VI)] elimination from Cr-contaminated wastewater. Optimisation process was achieved in order to obtain the optimum conditions that help achieving the highest Cr(VI) removal efficiency. For instance, One Factor At a Time ‘OFAT’ experiments were performed for the determination of the coded factors levels (low/high levels) that can be included in the Full factorial design experiment ‘many interacted factors at a time’. Afterwards, a small reactor design was implemented to develop Nostoc sp. algal biofilm. After that, the algal biofilm was applied in the Cr(VI) removal process to facilitate harvesting and dewatering of the biomass after the treatment process. Results showed that, live planktonic Nostoc sp. achieved the highest Cr(VI) removal efficiency of 98.16%at 100 ppm after 7 days contact time. Furthermore, Nostoc sp. stated its great ability to form a biofilm on polystyrene substrate which achieved the highest Cr(VI) removal of ‘86.498%’ at a concentration of 100 ppm after 7 days contact time. Some characterisation techniques such as Fourier Transform Infrared spectroscopy (FT-IR) and Scanning Electron Microscopy (SEM) analyses were applied on the developed biofilm of Nostoc sp. Isotherm and kinetics were investigated for the Cr(VI) removal process using Nostoc sp. biofilm.